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DEFENCE secretary Michael Fallon has admitted the gamble to use ‘risky’ new engine technology for the navy’s £6bn fleet of destroyers has backfired.

In a letter to the government’s defence committee, the former minister for Portsmouth said a raft of malfunctions and failures had been identified in the Type 45s’ engine and propulsion systems.

The lessons of choosing simpler, more robust design architecture and investing in earlier, more comprehensive shore testing have been applied in the Queen Elizabeth Class and Type 26 (Global Comabt Ship) propulsion designs

Michael Fallon, defence secretary

Yet, despite this, the government refused to go back to the drawing board, instead taking a gamble on being able to fix the errors early into the life of the destroyers.

Mr Fallon’s letter comes weeks after the MoD revealed in January the fleet of six Portsmouth-based warships would need a major refit on their engines which is expected to run to tens of millions of pounds after a string of power failures.

The move to overhaul the £1bn-a-piece air defence destroyers comes just seven years after the first vessel was commissioned.

In his letter to the defence committee, Mr Fallon said the former defence secretary Geoff Hoon had acknowledged at the time that using the new Rolls-Royce gas turbine engine ‘presented a greater degree of risk’ than the tried and tested LM2500 engine.

He said the first signs of performance and reliability ‘shortfalls’ emerged during shore testing in 2005, but claimed this ‘was not unexpected given the novel and complex nature’ of the system.

In 2007, after efforts to sort the errors, the trials of HMS Daring revealed a further crop of ‘multi-layered defects’.

Mr Fallon wrote: ‘The system did not meet the expected level of reliability and industry identified and implemented improvements in system configuration, tuning and reliability.’

Between the first Type 45 launch in February 2006 and the last one in October 2010, some 50 design changes had been made.

However, Mr Fallon explained to the defence committee the complexity of all the faults in the state-of-the-art system had ‘masked the true extent of the inherent design shortcomings’.

An independent study commissioned by the MoD in 2011 found that there was ‘no single root cause underlying the low reliability’ but a ‘large group of unconnected individual causes’.

In spite of these findings, the report still concluded the integrated full electric propulsion for the destroyers remained a ‘sound choice’ for the ships,’ – on the caveat its 16 recommendations to fix the issues were followed, Mr Fallon stated in his letter.

By 2013 – eight years after the first indication of faults – and with all the report’s modifications applied, it was realised that operating the ship while running just the Rolls-Royce WR21 gas-turbine was ‘flawed’.

Mr Fallon told the committee the turbine could not deliver the desired reliability.

Since 2014 a scheme called Project Napier has been in operation designed to improve reliability.

Mr Fallon was unable to say the exact number of breakdowns the destroyers had suffered throughout this period but stressed failure rates are now ‘one third of those experienced in 2010’.

He added that the costly lessons from the Type 45 fiasco had been learnt.

‘The lessons of choosing simpler, more robust design architecture and investing in earlier, more comprehensive shore testing have been applied in the Queen Elizabeth Class and Type 26 (Global Combat Ship) propulsion designs,’ he said. He added that even though there had been a number of breakdowns within the Type 45 class, the ships remained ‘hugely capable’ and that they were making ‘an enormous contribution to the defence of the UK and (its) international partners’.

HMS Defender is currently deployed in the Gulf supporting US carrier operations against Isil terrorists across Syria and Iraq. As well as HMS Daring, the other Type 45s are Diamond, Duncan, Dragon and Dauntless.